This invention relates to lubricating oil compositions for use as crankcase lubricants in internal combustion engines, and more particularly to hydrocarbon oil compositions which can reduce fuel consumption of internal combustion engines operated using said lubricating oil in the crankcase of said engine.
The trend today in the design of new internal combustion engines, and particularly those engines employed for vehicular transportation, is toward increasing fuel economy to conserve rapidly depleting hydrocarbon resources. Further there is great need for improved lubricants which can further reduce fuel consumption of existing engines, and particularly spark-ignition internal combustion engines.
Owing to the improvements in mechanical design over the years most engines in use today require but a small portion of fuel consumed to overcome friction. For example, it has been estimated that a modern vehicular gasoline engine being operated to cruise at e.g. 88 km/h (55 miles per hour) would consume only about eight percent of the fuel to overcome internal friction; with the remainder of the heat energy of the fuel going primarily to the coolant, exhausted gases and to work output of the engine. Accordingly, fairly substantial improvement in crankcase lubricant frictional properties will be required to reduce fuel consumption by even one or two percent for a given work output of the engine. Moreover, such improvement must be accomplished without adversely affecting other important properties of the crankcase oil such as detergency, antiwear and load-carrying properties.